Psoriasis: a disease of the total skin.

Psoriasis is a disease of the total skin, which becomes clinically evident when a psoriatic lesion appears following an injury to the symptomless skin of a psoriasis patient. Although not all biopsy specimens of the symptomless skin show pathologic findings, the evolution of a psoriatic plaque can be envisioned as developing from the nonvisible phases of residual psoriasis, prepsoriasis, and latent psoriasis into a visible state where macules evolve into papules and papules coalesce to form plaques.